EWP Blog – Page 5 – Spring Experiments & Beyond

Developing and Splitting Cells in Sterling County TX

Posted in GLM, GREMLIN, SPG2024 on May 22, 2024 by Kevin Thiel.

This lengthy post will cover a number of interesting observations with developing and splitting cells near Sterling County TX. This post will mainly focus on GREMLIN, but also a few other products.

Initially, we were focused on new updraft development Glasscock County TX. GOES-E GREMLIN (left panel) depicted Z values of about 57dBZ. KMAF comp reflectivity (right panel) was also picking up some 50+ dBZ. The 0.5 slice on KMAF (middle panel) was yet to really show anything of interest. This is evidence that GREMLIN is picking up on situations where echoes aloft have not yet started reaching near the ground. This has a degree of predictive value.

The loop from here shows that this storm then proceeds to split as it moves into Sterling County TX. The storm split is apparent on the KMAF lowest slice and comp reflectivity, as early as 2020Z. On GOES-E GREMLIN, the split does not start to show up until 2040Z, and is not readily apparent and clear until 2100Z.

So, let’s look a little closer into why GOES-E GREMLIN may have struggled with picking up the split. The loop below compares GOES-W satellite imagery (left panel) with GOES-E satellite imagery (right panel). While GOES-E data masks the updraft of the left-mover under the anvil from the right-mover, GOES-W has a better view of the left-mover updraft.

Comparing GOES-W GREMLIN and GOES-E GREMLIN, it’s clear that GOES-W had the better view of the left-mover updraft, and picked up on the split much more accurately (though it was low on dBZ values). On the contrary, GOES-W GREMLIN did a much less consistent job in handling the right-mover.

–Insolation

From a GLM perspective, it’s clear that GOES-West GLM sensor had a better view of the left split updraft and lightning activity than GOES-East. The flash extent density product shown below detected an increase in activity much quicker on GOES-West than its east counterpart. This may be due to the less inhibited view GOES-West had of the updraft looking at it from an angle compared to a more top-down view GOES-East had, which may have been blocked by water droplets or hail near the top of the thunderstorm.

-Joaq

Adding Latitude/Longitude on Dashboard May Help Locate Mistaken Entry

Posted in DSS, LightningCast, SPG2024 on May 22, 2024 by Kevin Thiel.

While doing DSS for the PGA tournament, there was an instance where we were uncertain whether the dashboard was matching the values on the map. Below, the probability of 1 flash and 10 flashes are shown. Using the sampling tool within the 10 mile range ring, the values never exceeded 50 percent. However, on the dashboard for the PGA Attempt 3, there were values above 70 for a single flash.

Trying to find the reason why, the most likely situation is that the forecaster may have mistyped, either mixing up decimal points in the lat/lon, or swapping two digits around. It may be helpful to be able to go back and edit the entry if that occurs or be able to view the lat/lon point to be certain whether a typo occurred putting in the entry.

In this case it wasn’t a typo – It was parallax!

Kadic

OCTANE… the GOAT for Warning Ops Today!

Posted in OCTANE Speed Sandwich, SPG2024 on May 22, 2024 by Kevin Thiel.

On the warning desk today, I’ve noticed that I have been using OCTANE the most out of the newer tools (besides an adjacent radar). It has really helped with confidence with warning decisions – are the storms maintaining strength… are newer ones growing? The storm in the eastern portion of this loop (below) has been going and going for a handful of hours (originally SVR in our area). OCTANE has kept right along with it and showing its evolution aloft (in both IR and Visible).

Also learning to use the CTP and CTD portion of OCTANE – it’s been helpful to keep track of the newer updrafts (shows up really well to the west with the outflow, but also in the green where there is more anvil/cirrus overflow). Also, it’s been a great tool to see where storms are maintaining strength (where the divergence signature in the pinks/purples hold on).

These products have aided in confidence in warning ops, especially with lack of primary radar.

Forecaster Cumulus

Comparing GREMLIN Across Two Storms

Posted in GREMLIN, SPG2024 on May 22, 2024 by Kevin Thiel.

The GREMLIN radar product is shown above in the top left while MRMS composite reflectivity is on the top right. The two storms in question have severe warnings on them in this loop. The thunderstorm in the southwest is more isolated from other convective cloud debris, while also displaying a more intense thermal couplet and cloud top divergence signal than the thunderstorm to the northeast. It seems likely that this is the reason why the northeast storm has a lower ceiling for GREMLIN reflectivity than the southwest storm, even though the MRMS composite includes a 60 dBZ core in the northeast storm.

-Joaq

OCTANE Cloud Top Divergence and Cooling to Analyze Thunderstorm Severity

Posted in OCTANE Speed Sandwich, SPG2024 on May 22, 2024 by Kevin Thiel.

The distribution characteristic of the derived cloud top divergence product has been helpful in highlighting potentially severe thundretsorms. Here the purple/pink colors are fairly consistent compared to the more “broken” distribution of colors to the east. Additionally, cloud top cooling is appearing as an overshooting top (and continued to reappear after this animation ended). Even if radar data was absent the severity of the thunderstorm would be apparant. A warning was issued on this storm (shown below).

-Joaq

Comparing PHS Reflectivity with the HRRR and MRMS Reflectivity

Posted in PHSnMWnABI, SPG2024 on May 22, 2024 by Kevin Thiel.

In this animation we track the progression of MRMS composite reflectivity (right) hourly over the previous three hours compared to the PHS (left) and HRRR (center) reflectivity. This morning convection allowing models were slow to initiate convection compared to reality and it seems that trend is continuing this afternoon with the southeastern progression of ongoing convection. The PHS has been slowest today with the southeastern movement, while the HRRR is a bit closer to reality but still behind (especially in the in the northeastern portion of the CWA.

-Joaq

Using GREMLIN for Time of Arrival

Posted in DSS, GREMLIN, LightningCast, SPG2024 on May 22, 2024 by Kevin Thiel.

LightningCast has been running high near the PGA Tournament today near Fort Worth as a result of several thunderstorms around the region, but not over the region. As a result, decided to swap over towards trying to use GREMLIN to find the time of arrival of the boundary noted earlier.

So an attempt was made to highlight this in the DSS image to provide an estimate of when these hazards would arrive. Perhaps another proofread would’ve caught the initial typo from copying it over. However, a value of about 40 percent was noted. Partners still had information that storms would become increasingly likely over a narrower time frame in addition to the probabilistic information from LightningCast.

But nature had other plans with a strike and a few pulses of lightning over the event at the time this was “sent out”. An area of weak convection was in the area, and so I would’ve thought that this would not produce lightning.

Sneaking in information on the RGB evaluation, you can see how this was not a young storm and likely something in decay, and that may track with a bit of the surprise element.

Kadic

Speed of Incoming Surface Boundary

Posted in PHSnMWnABI, SPG2024 on May 22, 2024 by Kevin Thiel.

One of the things that we noticed was that it appears that model guidance is too slow dropping a weak surface boundary to the south. As a result the convection in model guidance is likely being developed too far to the north of what is likely to actually occur.

Below is the surface winds from the PHS model forecast from the 17z run for 20z. It has a boundary that is near or north of the Texas-Oklahoma border.

In reality, the boundary has been a bit further south. However, this has been the theme of the day, with convection generally advancing east faster than most high-resolution model guidance. Below are the surface observations across Texas showing how much further south the boundary is, in addition to the fact that the wind field is stronger than what PHS is indicating.

The image below has the forecast model composite reflectivity (top right) nearly a degree longitude to the west of MRMS radar reflectivity (bottom right).

This raises additional concerns, as out ahead of the convection, the PHS forecasts an increase in SRH. If this is unchanged considering the current placement of convection, it may indicate a greater probability of storms rotating. The fact that we’re also seeing a sharper boundary present in the wind field suggests we could also see stronger convergence along the band of developing convection than may be indicated within the PHS forecast.

Kadic

Using OCTANE to diagnose three convective environments along the Missouri border

Posted in OCTANE Speed Sandwich, SPG2024 on May 21, 2024 by Kevin Thiel.

Currently monitoring OCTANE data in the vicinity of the Missouri border at about 1850Z on Tuesday, May 24.

North of the border (far southwest Iowa) there is mature convection, with a clear signal for changes in direction and speed on the anvil (top two panes). The mature convection shows cloud top divergence, with new convection on the southern flank showing a sharp signal for cloud top cooling (bottom left).

There is an area of banded cirrus moving through the region just south of this. This cirrus shows up on day cloud phase imagery (bottom right) but also in the OCTANE speed product. Looking at satellite data qualitatively, it’s clear the cumulus field is much less impressive in this area. Convection is not yet initiating here. Surface observations don’t show a clear signal for a less favorable air mass, so it’s possible the mid-level conditions are not as favorable.

South of all of this, we are looking at a new area of updraft initiation occurring just on the Kansas side of the border. On conventional satellite imagery we can see updrafts reaching upper levels and shearing off (orphaned anvils) indicating true convective initiation is still a little ways off, but we are getting very close. There is a consistent signal on OCTANE cloud top cooling for some of these spotty updrafts. Comparing with conventional imagery, the OCTANE cloud top cooling signals provided 5-10 minutes of lead time on the orphaned anvils. This is useful information, as once these storms begin maturing, they may provide a little more lead time on the initiation of lightning in addition to just the initiation of mature updrafts.

–Insolation

Storm Hopping Over Subarray

Posted in GLM DQP, SPG2024 on May 21, 2024 by Kevin Thiel.

We noticed a change in the storm on GLM as it tracked northeast. GLM seemed to decrease as the storm passed through the subarray region, but the number of flashes remained relatively the same according to the ground network. Knowing the location of this subarray and also comparing GLM to the ground network gave us confidence that the dip in GLM was not due to a reduction in flashes/storm intensity.

Cumulus and Kadic